People who have air traveled with breast pumps

I am taking a plane trip for the first time after giving birth. I will not be taking my baby (who will be 3 1/2 months) as it's only 2 days. So I will be bringing my spectra 1 and pumping while I'm away.

I've researched online about checking with the airlines to see if it qualifies as a medical device and also about declaring the milk I pump with TSA.

But I'd like to hear from anybody who has actually done this before. Did you have problems? Were they nice about it? Do they test every container of milk or just one at random? If I can bring it totally frozen in a cooler will it be easier? Anything else I should know or any useful tips would be appreciated!